Cholelithiasis is thought to develop from the formation of saturated or supersaturated solutions of cholesterol in bile. The objectives of this research are to examine the preparation and properties of metastable solutions of cholesterol in model bile systems. Various methods of preparation of the metastable solutions will be investigated, and static and scanning calorimetric techniques will be used to monitor crystallization of the cholesterol and to examine the basic thermal properties of the solutions and related paracrystalline phases. Stability and heat capacity functions of the phases will be correlated with variation of the basic composition of bile components, cholesterol, bile salts, and lecithin. Also, alterations in the media pH, ionic strength and ionic composition will be related to the basic properties of the phases. Hopefully, the results of these studies can shed light on the complex problem of formation of cholesterol gallstones in the gall bladder.